Dehumidifying apparatus



Aug. 1, 1950 w. L. MOGRATH 2,517,499

DEHUMIDIFYING APPARATUS Filed May 14, 1947 FlG.l

- INVEN TOR. 4- m M BY 4 Patented Aug. 1, 1950 DEHUMIDIFYING APPARATUS William L.,McGrath, Syracuie, N. Y., asaignor to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Application May is, i947, Serial No. 748,037 7 Claims. (01. 62-140) 1 This inventionrelates to dehumidifying apparatus and more particularly to apparatus employing refrigeration for the removal of moisture from air being conditioned without substantially affecting the sensible heat of such air.

The chief object of the present invention is to provide dehumidifying apparatus employing refrigeration to remove the latent heat of a, stream of air being conditioned without substantially affecting the sensible heat of such air stream.

object of the present invention is to provide dehumidifying apparatus including a plurality of porous tubes disposed in the path of air being conditioned, the porous tubes forming a portion of a, closed circuit for the passage of cooled air, the passage of cooled air through the porous tubes establishing a decrease in vapor pressure in the interior of the tubes whereby vapor from the air being conditioned penetrates the tubes to the interior thereof, and is carried away by the passage of cooled air through the tubes.

A further object is to'provide dehumidifying equipment for air to be conditioned capable of efiecting the removal of latent heat from the air without substantially affecting the sensible heat of the air, such equipment including a passageway for air to be conditioned, a closed circuit for cooled air having a portion thereof disposed in the path of the air being conditioned and a refrigeration system having its evaporator disposed within the closed circuit to cool air circulating therein and to remove moisture therefrom. The cooled air, having a vapor pressure less than the vapor pressure of the air being conditioned, permits vapor to migrate from the air being conditioned to the cooled air thus removing vapor from its sensible heat. Other objects of my invention will be readily perceived from the following description.

The present invention relates to apparatus for removing vapor from air and comprises in combination a casing forming a passageway for air to be conditioned, means for passing air through said passageway, a, porous member, air directed the conditioned air without affecting substantially Figure 1 is a diagrammatic view illustrating the dehumidifying apparatus of the present invention; and

Figure 2 is a fragmentary isometric view illustrating the closed circuit for cooled air.

Referring to the drawing, there is shown a casing 2 forming a passageway for air to be conditioned. Dampers 3 are provided incasing 2 to permit exterior or outside air to be drawn within casing 2 by blower or fan 4 and distributed to areas being conditioned.

Filter 5 is disposed within the casing to filter dust and dirt particles drawn within casing 2. The equipment 5 for dehumidifying air drawn within casing 2 is also disposed in casing 2, as

hereinafter described. If desired, a suitable heat exchange member such as a coil I may be disposed in casing 2 for treating the air after moisture has been removed therefrom.

The dehumidifying' equipment comprises a closed circuit illustrated generally at 9. Closed circuit 9 includes a, plurality of porous tubes l0 disposed within casing 2. Tubes l0 are connected by duct ii to a casing 12 including evaporator i3 of}; refrigeration system ,hereinafter described. A duct 15 connects casing I: with tubes in permitting cooled air tobe circulated by means of blower l6 through duct I5 to the tubes to, through tubes l0 and returned through duct H to casing I2, passedthrough evaporator 53 to remove moisture therefrom, again being directed through circuit 5 as described.

While Figure 1 illustrates the dehumidifying equipment 6 diagrammatically. it will be understood that equipment 6 includes the complete dehumidifying unit including the evaporator l3 ofrefrigeration system ll; theunit may be disposed in casing 2 in whole or in part. As shown diagrammatically in Figure 1 for ease of illustration, onlt a p rtion of the complete unit is disposed in casing 2, such portion including part of through the passageway contacting one side of said member, the pores of said member permitting passage of vapor through the wall thereof while being substantially resistant to the passage of air, means for passing a fluid medium'over the opposite side of said member, and means for removing moisture from the fluid medium.

The attached drawing illustrates a preferred embodiment of my invention in which duct 95, tubes I0, and part of duct H, as shown in Figure 2. l

Tubes ill may be composed ofhighly porous fused alumina such as Alundum obtained by electrically fusing bauxite. The tubes are so formed that the, pores thereof are of such size as to permit the passage of vapor through the walls thereof while being substantially resistant to the passage of air. Additionally, such tubes are satisfactory heat insulators; therefore, the air being conditioned, in passing through the tubes will have its dewpoint lowered by migration of moisture therefrom with slight change in the l dry bulb temperature of such air. Tubes Ill may be manufactured to meet any required condition by varying the pore size, grain size, permeability and density thereof.

It will be appreciated moisture is removed from the cooled air..by evaporator l3 disposed within the closed circuit 9. The cooled air is passed through tubes In by blower l6, vapor pressure within-the interior of the tubes being less than the vapor pressure of the air being conditioned exterior of the tubes. Accordingly, vapor in the air being conditioned migrates through the pores of the tubes to the cooled air within the interior of the tubes: passage of cooled air through the interior of the tubes carries away such vapor, the vapor being removed from the cooled air by its passage in heat exchange relation with evaporator IS. The removal of vapor from the air being conditioned reduces the latent heat of such air without substantially affecting the sensible heat of the air.

Refrigeration system l4 includes a compressor I! connected to a condenser l8 by discharge line It. A receiver 20 receives liquid refrigerant from the condenser It, the liquid refrigerant being supplied through liquid line 2| to evaporator l3. Expansion valve 22 is disposed in line 2| to meter the quantity of refrigerant supplied to the evaporator inaccordance with the load imposed thereon. Expansion valve 22 is controlled by means of a bulb 23 disposed adjacent suction line 24 connecting evaporator l3 and compressor H.

In operation, air to be conditioned is drawn into and through casing 2 by means of blower I, treated to remove vapor therefrom and distributed to the areas being conditioned. Cooled air having a desired low dew-point is directed through circuit 9 by blower l6, passing throu h tubes III disposed in casing 2. Air to be conditioned flows transversely across tubes IO' and is in direct contact with such tubes as disclosed above. The tubes it are porous as described above, the pores being of such size as to transmit water vapor while being relatively resistant, to the flow of air through the wall of the tube. As the low dewpoint air stream is directed through the interior of tubes iii, the relatively higher dew-point air stream to be conditioned flows over the exterior surfaces of tubes Ill and permits migration of water vapor from the exterior to the interior of the tubes. Such vapor is absorbed by the cooled air stream passing through the interior of the tubes and is subsequently removed when such air is again passed in heat exchange relation with evaporator ll of refrigerating system H. The removal of water vapor from the air stream being conditioned is conducted without a corresponding removal of sensible heat. As pointed out above the walls of tubes l form satisfactory heat insulators to insulate one stream of air from the second stream of air. Air being conditioned, in

passing through casing 2, will have its dewpoint and wet bulb temperature decreased with relatively small change in the dry bulb temperature.

During operation of the closed circuit to remove vapor from the air being conditioned, the refrigerating system H continues to supply refrigerant to evaporator l3 disposed in the closed circuit 9; such refrigerant is placed in heat exchange relation with air circulating therein and serves to cool the same and remove moisture carried thereby from the portion of the circuit in contact with the air being conditioned.

It will be appreciated other fluids than air may be employed in circuit 9. Since circuit 9 is closed, obviously other gases may be used therein to provide improved economy. For certain uses, it may be desirable to employ liquid as well as gases.

In a conventional dehumidifying system employing refrigerating equipment all of the air to be conditioned must be cooled to the desired dew-point to remove moisture. So doing, reduces the dry bulb temperature to the same low point. If it be desired to obtain dry'air without sensible cooling, such air must be; reheated. This procedure creates operating loss and increases initial cost 01" equipment because it requires refrigeration capacity suflicient to remove both sensible and latent heat. In addition, heat must be again supplied to reheat the conditioned air to the desired temperature. The present invention eliminates the operating loss and permits a considerable decrease in the initial cost of equipment for latent heatmay be removed from air to be conditioned with only a relatively small decrease in sensible heat.

The present invention provides simple and economical equipment for removing moisture from air being conditioned without substantially affecting the dry bulb temperature of the air. The present invention reduces the required refrigeration capacity for the total volume of air being conditioned need not be reduced substantially in dry bulb temperature to remove moisture therefrom. Only a small volume of air need be cooled and that only through a small range, such air being employed to carry away vapor from the air being conditioned. The present invention permits the removal of latent heat without substantially affecting the sensible heat of the air being conditioned. If desired, the sensible heat of the air being conditioned may be modified after the vapor (latent heat) has been removed.

While I have described a preferred embodiment of my invention, it will be understood my invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. In apparatus for removing vapor from air the combination of a casing forming a passageway for air to be conditioned, means for passing air through said passageway, a plurality of porous members disposed in said passageway in the path of air directed therethrough, the pores of said members permitting passage of vapor through the walls thereof while being substantially resistant to the passage of air, means for passing a second air stream through said members, refrigerating equipment for removing moisture from the second air stream, vapor pressure within said passageway exteriorly 01' said members being greater than the vapor pressure interiorly of said members, whereby moisture from the air being conditioned migrates into the interior of said members and is removed by the passage of said second air stream through said membersand means connecting the refrigerating equipment to said members permitting the second air stream to circula therethrough.

2. In apparatus for removing vapor fr un air, the combination of a casing forming a passageway for air to be conditioned, means for parsing air through said passageway, a plurality of porous members disposed in said passageway in the path of air directed therethrough, the pores of said members permitting passage of vapor through the walls thereof while being substantially resistant to the passage of air, means for passing a second air stream through said members, refrigerating equipment including an evaporator disposed in heat exchange relation with the second air stream for removing moisture therefrom, ducts connecting the evaporator with said members to permit the second air stream to pass through the evaporator and then through said members returning to the evaporator, vapor pressure exteriorly of said members being greater than vapor pressure interiorly of said members whereby moisture migrates from the air being conditioned through the pores of said members into the interior of said members and is removed by the passage of the second air stream therethrough.

3. Apparatus according to claim 1 in which the porous members comprise fused alumina tubes, the pores of said tubes being of such size as to permit passage of vapor therethrough while being substantially resistant to the passage of air.

4. Apparatus according to claim 2 in which a blower passes air through said passageway, a second blower passes air through said porous fused alumina tubes, and the refrigerating equipment comprises a compressor-condenser-expander system, the evaporator disposed in heat exchange relation with the fluid medium forming the expander of the system.

5. In apparatus for the removal of latent heat from air to be conditioned without substantially affecting the sensible heat of the air, the combination of a casing forming a primary air passage for air to be conditioned, means for directing air through said passage, a closed circuit for the passage of conditioned air having a low dewpoint, said circuit including a plurality of porous fused alumina tubes disposed in said primary passage, the pores of said tubes being of such size as to permit passage of vapor through the walls thereof while being substantially resistant to the passage of air, means for circulating air through said closed circuit, a refrigeration system having its evaporator disposed in said circuit in heat exchange relation with air circulating therethrough to cool such air thereby condensing and precipitating moisture therein, vapor in the primary passage exteriorly of said tubes penetrating the tubes to the interior thereof and being removed by the passage of the conditioned air through the tubes whereby latent heat is removed from the air being conditioned in the form of vapor without substantially afiecting the sensible heat of the air being conditioned, the removed vapor being carried 011 by the circulation of conditioned air through the tubes and being condensed and precipitated by the evaporator for removal from the system.

6. In a method of removing latent heat from air to be conditioned without substantially afiecting the sensible heat of the air, the steps which consist in cooling a first. stream of air to condense and precipitate water vapor present therein, and passing the cooled stream of air in a closed circuit within the path of a second stream of air being conditioned and separated from the second stream by a plurality of separate porous walls permeable to vapor and substantially resistant to the passage of air whereby vapor within the second stream of air migrates to the first stream of air.

7. In a method of removing latent heat from air .to be conditioned without substantially afiecting the sensible heat of the air, the steps which consist in cooling a first stream of air to condense and precipitate water vapor present therein, passing the cooled stream of air in a closed circuit within the path' of a second stream of air being conditioned and separated from the second stream by a plurality of porous fused alumina Walls permeable to vapor and substantially resistant to the passage of air whereby vapor within the second stream of air migrates to the first stream, cooling the first air streamto remove the carried moisture, and again directing the first air stream through the closed circuit within the path of the second stream.

WILLIAM L. McGRATH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,261 Hopkins Aug. 10, 1937 2,223,586 Thomas Dec. 3, 1940 2,336,456 Anderegg Dec. 14, 1943 2,405,812 Binder Aug. 13, 1946 

